The sleep of cetaceans (the dolphins and toothed whales) has unique properties that may provide important insights into the evolution and function of sleep. Cetacean sleep may also allow us to differentiate between the behavioral roles of the several neurotransmitter systems that have been implicated in sleep and arousal. One of the unusual properties of cetacean sleep is the presence of long periods of "unihemispheric slow wave sleep" (USWS). A number of species of cetacean have been examined and all have only USWS, i.e. both hemispheres never show high voltage activity at the same time. Another unusual feature of cetacean sleep is the apparent absence or perhaps the near absence of REM sleep. If cetaceans do not have REM sleep, they would be the only mammals lacking this state. In the proposed studies, we will determine the nature of the changes in sensory and motor function during USWS in the bottlenose dolphin and beluga whale. We will present lateralized and not lateralized stimuli of different modalities to dolphins and whales adapted to sleep in stretchers to determine if sensory thresholds are altered ipsilateral and contralateral to USWS. We will measure the release of serotonin, norepinephrine, acetylcholine, and hypocretin bilaterally with cortical microdialysis and determine whether all or any of these transmitters have asymmetrical release during USWS. We will use telemetry and digital recorders to search for evidence of REM sleep in freely swimming cetaceans, monitoring the EEG, EMG, EOG and autonomic signs of REM sleep, including muscle jerks, rapid eye movements, and erections. We will determine whether the "jerks" that have been observed are signs of REM sleep, arousal or myoclonus. We will search for REM sleep-like periods of reduced monoamine release in dolphins and whales sleeping in stretchers. We will investigate the neuroanatomy of the brainstem and forebrain aminergic, cholinergic and hypocretin cell groups involved in behavioral state control in cetaceans. The proposed studies take advantage of a rapidly vanishing opportunity to study cetacean sleep. They will improve our understanding of the physiological and neurochemical substrates of mammalian sleep.